linux-kernel - Re: [PATCH] CIFS: use the correct length when pinning memory for direct I/O for write

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Date:   Sun, 16 Dec 2018 15:10:35 -1000
From:   Joey Pabalinas <joeypabalinas@...il.com>
To:     longli@...rosoft.com
Cc:     Steve French <sfrench@...ba.org>, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org,
        linux-rdma@...r.kernel.org, stable@...r.kernel.org,
        Joey Pabalinas <joeypabalinas@...il.com>
Subject: Re: [PATCH] CIFS: use the correct length when pinning memory for
 direct I/O for write

On Sun, Dec 16, 2018 at 11:17:04PM +0000, Long Li wrote:
> From: Long Li <longli@...rosoft.com>
> 
> The current code attempts to pin memory using the largest possible wsize
> based on the currect SMB credits. This doesn't cause kernel oops but this is
> not optimal as we may pin more pages then actually needed.
> 
> Fix this by only pinning what are needed for doing this write I/O.
> 
> Signed-off-by: Long Li <longli@...rosoft.com>
> Cc: stable@...r.kernel.org

Looks sane to me.

Reviewed-by: Joey Pabalinas <joeypabalinas@...il.com>

> ---
>  fs/cifs/file.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 3467351..c23bf9d 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2617,11 +2617,13 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
>  		if (rc)
>  			break;
>  
> +		cur_len = min_t(const size_t, len, wsize);
> +
>  		if (ctx->direct_io) {
>  			ssize_t result;
>  
>  			result = iov_iter_get_pages_alloc(
> -				from, &pagevec, wsize, &start);
> +				from, &pagevec, cur_len, &start);
>  			if (result < 0) {
>  				cifs_dbg(VFS,
>  					"direct_writev couldn't get user pages "
> -- 
> 2.7.4
> 

-- 
Cheers,
Joey Pabalinas

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